1. Field of the Invention
The invention relates to the field of charge transfer devices, particularly bucket-brigade devices.
2. Prior Art
The bucket-brigade device (BBD), despite certain advantages over the charge-coupled device (CCD) has received much less attention than the CCD. The most important advantage of the BBD is the simplicity and flexibility of tapping the signals along the device. This ability is particularly important for correlators and transversal filters, as well as for interfacing with peripheral circuitry. Another advantage of the BBD is its compatability with existing MOS processing. As a result, a wealth of circuits used in making memories and microprocessors can be integrated on the same substrate with the BBD. The development of modern MOS technology, along with the tetrode gate BBD structure which reduces the effects of channel-length and barrier-height modulations, make the performance of the BBD very comparable with its CCD counterpart in the low frequency range.
As will be seen, the present invention provides a BBD with more efficient charge transfer, which improves the low frequency and high frequency performance of the device. The specific prior art aspects of the BBD which are affected by the invented structure, are described in conjunction with FIG. 1 and with reference to the closest prior art device known to applicant, that shown in U.S. Pat. No. 4,157,558.